The goal of the research herein proposed is elucidating cellular phenomena associated with experimental epilepsy. To this end the effects of convulsant drugs on identified invertebrate neurons and synapses are being studied in an effort to associate differences in drug responsiveness with differences in the physiological biochemical and anatomical characterisitcs of the cells. The information thus gained is expected to narrow the range of cellular mechanisms on which it is probable that particular drugs exert their actions. Cellular phenomena associated with epileptogenesis in mammaliam neuron systems are similar to those produced by drugs in invertebrate neurons. Because technical factors restrict intracellular neurophysiological study of drug actions in higher nervous systems, use is being made of a group of identified neurons in the central nervous system of the leech. These cells share the same environment, have known functions, and are synaptically related; a large and growing body of precise information about them is available for comparison will their drug responses.